/**
 * Licensed to DigitalPebble Ltd under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * DigitalPebble licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.digitalpebble.stormcrawler.filtering.regex;

/**
 * A generic regular expression rule. Borrowed from Apache Nutch 1.9.
 */
public abstract class RegexRule {

    private final boolean sign;

    /**
     * Constructs a new regular expression rule.
     * 
     * @param sign
     *            specifies if this rule must filter-in or filter-out. A
     *            <code>true</code> value means that any url matching this rule
     *            must be accepted, a <code>false</code> value means that any
     *            url matching this rule must be rejected.
     * @param regex
     *            is the regular expression used for matching (see
     *            {@link #match(String)} method).
     */
    protected RegexRule(boolean sign, String regex) {
        this.sign = sign;
    }

    /**
     * Return if this rule is used for filtering-in or out.
     * 
     * @return <code>true</code> if any url matching this rule must be accepted,
     *         otherwise <code>false</code>.
     */
    protected boolean accept() {
        return sign;
    }

    /**
     * Checks if a url matches this rule.
     * 
     * @param url
     *            is the url to check.
     * @return <code>true</code> if the specified url matches this rule,
     *         otherwise <code>false</code>.
     */
    protected abstract boolean match(String url);

}
